Preheat oven to 300°.
Place corned beef brisket in a large Dutch oven. Top with onion, chicken broth, pickling spice, kosher salt and garlic cloves. Add enough water to cover brisket. Cover with lid and bake for 2 hours.
Remove from oven. Increase oven temperature to 350°. Add carrots and mini whole potatoes. Make sure that your meat, potatoes and carrots are all submerged in liquid. Add additional water if needed. Cover and return to oven. Cook for an additional hour.
After the brisket has cooked for 3 hours, remove from oven and add cabbage wedges. Cover and cook for another 30 minutes or until cabbage, potatoes and carrots are soft.
Carefully remove from oven and allow meat to rest for 10-15 minutes.
To serve, slice brisket against the grain. Place on platter with vegetables. Top vegetables with softened butter. Sprinkle dish with finely chopped parsley or chives. Serve with crusty bread and whole grain mustard.
